A light-emitting device utilizing a light-emitting semiconductor such as light-emitting diode (LED) that has been widespread in recent years is normally produced by a method in which a light-emitting semiconductor (LED) is fixed on a lead frame of a molded product obtained by integrally molding a synthetic resin as a reflector in the shape of a concave on a lead frame, followed by sealing with a sealant such as an epoxy resin or a silicone resin.
As the material for a reflector, Patent Document 1 discloses a composition that provides a cured product excellent in heat resistance and weatherability, as well as in adhesiveness with peripheral components, which is obtained by mixing a thermoset resin such as an acrylate resin with a white pigment such as titanium oxide.
When titanium oxide as a representative white pigment is used, the viscosity of a thermosetting composition tends to increase, and the fluidity of the thermoset resin liquid is deteriorated. If the fluidity of the liquid is poor, when a resin molded product is formed in a lead frame, bending or un-filling of a reflector, formation of voids or burrs in a lead frame molded body occur, and hence mass producibility of a light-emitting device becomes insufficient. Further, it is required that only a slight effect be exerted on continuous moldability if a thermosetting composition is stored at normal temperature.